Android Settings Fragment

Question

I'm trying to add a settings fragment to my android-app. So, I added a xml-file and this activity: ``` public class SettingsActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Display the fragment as the main content. getFragmentManager().beginTransaction() .replace(android.R.id.content, new SettingsFragment()) .commit(); } public static class SettingsFragment extends PreferenceFragment { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Load the preferences from an XML resource addPreferencesFromResource(R.xml.preferences); } } } ``` It's being called from the onOptionsItemSelected function in the main activity: ``` if (id == R.id.action_settings) { Intent intent = new Intent(this, SettingsActivity.class); startActivity(intent); return true; } ``` So, now, when I try to open the activity from the menu, it force-closes and I get this error in the console: ```…

Accepted Answer

You are replacing a fragment that never added before…

```
getFragmentManager().beginTransaction()
            .replace(android.R.id.content, new SettingsFragment())
            .commit();
```

try

```
            .add(android.R.id.content, new SettingsFragment())
```

But the right code should be (pseudo code)

- Find fragment by id or tag

- If found fragment is null, then create one.

You can find plenty of examples around the net and stackoverflow. ;)

UPDATE Ok, here's some sample code for you to use as a starting point.

Assumptions: You use the same activity for more than one fragment, so you need to either restore an existing or create a new one.

```
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
Fragment newFragment = fm.findFragmentByTag("Some_Tag");
if (newFragment == null) {
     newFragment = SomeFragment.newInstance(); //create a new frag
}
// Find the old one to know if we have to replace or simply add to this container
Fragment oldFragment = fm.findFragmentById(R.id.content_container);
if (oldFragment != null) {
    ft.replace(R.id.content_container, newFragment, "Some_Tag");
} else {
    ft.add(R.id.content_container, newFragment, "Some_Tag");
}
// optionally use a nice transition
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
// …and to the backstack if you wish…
ft.addToBackStack(null).commit();
```

If on the other hand you just want the simple version without anything fancy…

```
FragmentManager fm = getSupportFragmentManager();//if using support lib
Fragment fragment = fm.findFragmentById(R.id.your_container);
if (fragment == null) {
   fragment = YourFragment.newInstance();
   fm.beginTransaction()
   .add(R.id.your_container, fragment, "some_tag_if_you_wish_to_use_find_by_tag_later")
   .commit();
}
```

This will only add the fragment if the container doesn't have it. Otherwise nothing remains to be done because the container already has your fragment. :)

Android Settings Fragment

Solution

Problem